This invention relates to a process control valve, automatic or manual, having integrated therewith a plurality of sensors for sensing various physical parameters of the fluid flowing through the valve, and a utilization device for controlling operation of the valve and/or displaying representations of the parameters.
Control valves, used in a variety of environments not only to control the flow of fluids (liquids and gases), but also to regulate pressure and temperature of fluids in fluid processing systems, are a special type of valve having a power positioning actuator which is responsive to externally supplied signals for operating (moving) a throttling or closure mechanism located in the valve body. Typical of such valves are rotary valves (ball, plug, eccentric disk, etc.) and linear valves (globe, gate, etc.). An exemplary globe-type control valve includes a valve body having an internal passage formed therein with an inlet opening, for receiving fluid, an outlet opening, for discharging fluid, and a central opening located in the valve body between the inlet opening and outlet opening and forming a valve seat. A valve stem, with a valve plug located on one end thereof, is disposed to extend into the valve body and is movable to selectively move the plug onto and off from the valve seat to thereby close the central opening and stop the flow of fluid, or unclose the central opening and allow the flow of fluid, respectively. The other end of the valve stem, opposite that on which the plug is located, is coupled to an actuator typically mounted on top of the valve body. The actuator includes a cylinder, and a movable piston disposed in the cylinder and coupled to the other end of the valve stem (or could include a diaphragm for operating the stem). A pressurized source of air is supplied to a positioner oftentimes located at the side of the actuator, and the positioner, in response to control signals, directs pressurized air to the cylinder both above and below the piston, to thereby cause the piston to move to selected positions in the cylinder and thus the plug to move to desired positions in the valve body.
By controlling the position of the plug in the valve body, upstream pressure, downstream pressure and temperature of the fluid flowing through the valve (as well as external variables such as pressure or volume of fluids in tanks connected into the system, pH of fluid in the system, etc.) can be controlled. Typical prior art methods for determining these upstream and downstream pressures and the temperature of the fluid have involved placing sensors in pipes joined both upstream and downstream to the valve. Flow rates through the valve have also been measured in prior art systems by inserting a flow meter into pipes leading to or coming from the valve. (It has also been proposed that flow rates be determined in microprocessor controlled valves by calculating the flow rates from flow characteristics of the valves and flow characteristics of the fluids. See U.S. Pat. No. 4,581,707). This sensed information could then be transmitted to a remotely situated control processor for processing which could, in turn, transmit signals back to the positioner to cause it to supply pressurized air to the cylinder of the actuator in an attempt to move the plug to positions in the valve body which would yield desired fluid flow parameters. Of course, with the sensors being located outside of the valve the, precision of the process being carried out would not be completely accurate.